A writer's ramblings ~~ including links to my
books, "Behind These Mountains, I, II and III, and to the Tenth Edition of the highly acclaimed comprehensive Free writing course:
ACCESS THE WORLD AND WRITE YOUR WAY TO $$$

Or Quotation marks .
You'll find answers to many punctuation questions, and other writing questions, so Punctuation Made Simple is an excellent website to bookmark.However, a word of warning ~ the three examples given for em dash were published in 1876, 1873, and 1719. The second one was originally written in French, and
English translations may have carried over French punctuation.

21st century punctuation backed only by examples from the 18th and 19th
centuries may have changed. Therefore, I suggest using Chicago Manual of Style for the current usage of punctuation in publishing.You'll find it at Chicago Manual of Style Online , and at Amazon.